This invention relates to an improved method for producing dextranase, an enzyme capable of degrading dextran. More particularly this invention relates to an improved method which provides a dextranase product essentially free of biological contaminants. Further, this invention provides a novel culture of a mutant microorganism capable of hyperproducing dextranase.
Dextranase is used to hydrolyze dextran found in cane sugar production allowing the processing of previously unusable sugar juice for the production of sucrose. Dextranase has also been employed for the production of a dextran product which has found use as a blood substitute or extender. Because of its ability to hydrolyze dextran, dextranase has also been found highly useful for hydrolyzing the dextran produced by action of microorganisms causing dental caries or tooth decay. Thus, the incorporation of dextranase into a tooth powder, toothpaste or other oral detergent is considered in the art to provide a preventative or curative for tooth decay.
There are many known microorganisms capable of producing dextranase including moulds, e.g. fungi belonging to the genera Penicillium, Aspergillus, Spicaria, Fusarium and Chaetomium; bacteria, e.g. Lactobacillus, Cellvibrio, Flavobacterium and the like, see for example, U.S. Flavobacterium and the like, see for example, U.S. Pat. Nos. 2,742,399; 3,663,371; 3,875,009; and 3,912,594. In addition, it has also been reported that certain strains of yeasts have activity for dextranase, particularly strains of Lipomyces starkeyi, Webb and Spencer-Martins, Canadian Journal of Microbiology, Vol. 29, pages 1092-1095, 1983. However, this yeast has not been considered for industrial production of dextranase because of the reported slow growth of the organism and difficulty of avoiding contamination from other microorganisms during growth. This organism appears to be essentially acceptable under FDA procedures and, hence, useful in food industry dextranase applications.
In view of this, an object of the present invention is a method for culturing Lipomyces under unique conditions favoring rapid growth and low possibility of contamination by other microorganisms. Another object of this invention is a method for producing dextranase under conditions indicated by the prior art to be unproductive on an industrial scale. A further object of this invention is a dextranase product which is produced under conditions essentially free from biological contamination. These and other objects will be more fully illustrated in the following description of the invention. A still further object is the discovery and provision of a novel culture of a Lipomyces mutant capable of hyperproducing dextranase under the conditions found favorable for industrial scale production and without biological contamination.